docs: def get_sourcefile(self):
          """
          the name of thie file this class was compiled from, or None if not
          indicated
  
          reference: http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.7.10
          """  # noqa
  
          buff = self.get_attribute("SourceFile")
          if buff is None:
              return None
  
          with unpack(buff) as up:
              (ref,) = up.unpack_struct(_H)
  
          return self.deref_const(ref)